1. Field of the Invention
The present invention relates to a controlling apparatus, a record medium and a method, in particular, to those suitable for a home network system of which a number of digital AV (Audio Visual) devices are connected through, for example, the IEEE (Institute of Electrical and Electronics Engineers) 1394 bus.
2. Description of the Related Art
In recent years, mutual connection specifications have been proposed as middle wear of a home network system named HAVi (Home Audio/Video interoperability Architecture). Such specifications are for integrally managing and controlling a plurality of digital AV devices.
In such a home network system, when a digital AV device on the controlling side (referred to as controlling device) of a number of AV devices uploads control software stored in a digital AV device on the controlled side (referred to as controlled device) through the IEEE 1394 bus, even if a number of digital AV devices manufactured by different manufacturers are connected, they are normally and mutually operated. However, such high end digital AV devices are equipped with respective internal clocks. Corresponding to time information obtained from the outside (for example, a digital satellite broadcast), time of their clocks is compensated. Hereinafter, such a function is referred to as time compensating function.
On the other hand, low end digital AV devices may not be equipped with such a time compensating function due to the restriction of the cost. When video data is dubbed between digital VCR devices connected through, for example, the IEEE 1394 bus, if time of their internal clocks deviates, the recorded picture deviates from the reproduced picture. Thus, before the video data is dubbed, time of their internal clocks should be compensated so that the recorded picture synchronizes with the reproduced picture.
Thus, it is preferred to uniformly manage time of the internal clocks of the individual digital AV devices of a home network system.